In plane switching mode liquid crystal display device

ABSTRACT

An in-plane switching mode LCD device is disclosed, in which high response time is obtained and residual images are prevented from occurring. The in-plane switching mode LCD device includes first and second substrates, common electrodes arranged on one of the two substrates in a substantially zigzag pattern, a pixel electrode arranged with a substantially zigzag pattern corresponding to the common electrodes roughly in parallel with the common electrodes, common electrode frames projected from a bent portion of the common electrodes, pixel electrode frames projected from a bent portion of the pixel electrodes, and a liquid crystal between the first and second substrates.

[0001] This application claims the benefit of Korean Patent ApplicationNo. 2000-50430 filed on Aug. 29, 2000, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a liquid crystal display (LCD)device, and more particularly, to an in-plane switching mode LCD devicethat has a substantially zigzag pattern electrode structure in whichhigh response time is obtained and residual images are prevented fromoccurring.

[0004] 2. Discussion of the Related Art

[0005] Recently, research into in-plane switching mode LCD devices isbeing performed to solve the problems of a twisted nematic (TN) mode LCDdevice having a narrow viewing angle.

[0006] Furthermore, research for improving viewing angle and color shiftcharacteristics is being performed by forming an electrode of thein-plane switching mode LCD in a substantially zigzag pattern.

[0007] A related art in-plane switching mode LCD device will bedescribed with reference to the accompanying drawings.

[0008]FIG. 1 shows a layout of the related art in-plane switching modeLCD device. FIG. 2 shows an enlarged view of a disclination region inthe related art. FIG. 3 shows an enlarged view of a region whereelectric field is uneven in the related art.

[0009] The related art in-plane switching mode LCD device includes agate line 1, a data line 2, a common line 3, a thin film transistor(TFT) 6, a plurality of common electrodes 4, and a pixel electrode 5.

[0010] The gate and data lines 1 and 2 are arranged on a substrate todefine a pixel region. The common line 3 is formed within the pixelregion in parallel with the gate line 1. The TFT 6 is formed in aportion where the gate line 1 crosses the data line 2. The TFT 6 has agate electrode (not shown) connected with the gate line 1 and a sourceelectrode connected with the data line 2. The common electrodes. 4 arearranged within the pixel region in a zigzag pattern in parallel withthe data line 2. The pixel electrode 5 is formed between the commonelectrodes 4 in a zigzag pattern within the pixel region. Also, thepixel electrode 5 is connected with a drain electrode of the TFT 6 andoverlaps the common line 3.

[0011] In the related art in-plane switching mode LCD device, if avoltage is applied from an external driving circuit, an electric fieldparallel to the substrate occurs between the pixel electrode 5 and thecommon electrode 4, so that liquid crystal molecules are rotated alongthe electric field, thereby displaying a picture image.

[0012] The related art in-plane switching mode LCD device having azigzag pattern electrode structure has the following characteristics dueto its electrode structure.

[0013]FIG. 2 is an enlarged view of a portion “K” of FIG. 1. In thisportion “K”, disclination occurs in which the liquid crystal moleculesdo not rotate. This is because the electrode structure has a zigzagpattern. As a result, dynamic residual images occur and response timeincreases.

[0014] In portions “A” and “B” of FIG. 2, the liquid crystal 7 movesdepending on a pretwist angle and a direction of electric field.However, in a portion “C”, where the pixel electrode 5 and the commonelectrode 4 are bent, the liquid crystal 7 does not move as no pretwistangle exists.

[0015] As described above, in case where the electrode structure has azigzag pattern, the portion of the liquid crystal moves not because ofthe electric field but in accordance with adjacent liquid crystals.

[0016] Particularly, since the liquid crystal 7 in the portions “A” and“B” has a driving direction opposite to that of its adjacent liquidcrystal 7 in the portion “C”, the liquid crystal in the portion “C” maynot be driven.

[0017] Furthermore, as shown in FIG. 3, in the in-plane switching modeLCD device having two domains, uneven electric field occurs in a region8 outside the bend of the common electrode 4 and inside the bend of thepixel electrode 5.

[0018] In other words, the electric field generated to be perpendicularto the common electrode 4 and the pixel electrode 5 has an unevenarrangement in the region 8 and thus is not perpendicular to the commonelectrode 4 and the pixel electrode 5. In such case, response time ofthe liquid crystal molecules is reduced and dynamic residual imagesoccur.

[0019] The related art in-plane switching mode LCD device has severalproblems.

[0020] In case where the electrode has a zigzag pattern to improveviewing angle and color shift characteristics, the liquid crystal may beoperated not by the electric field but by adjacent liquid crystalmolecules. In this case, the electric field may unevenly be arranged. Asa result, the response time becomes slower and the dynamic residualimages occur, thereby deteriorating characteristic of the liquid crystalpanel.

SUMMARY OF THE INVENTION

[0021] Accordingly, the present invention is directed to an in-planeswitching mode LCD device that substantially obviates one or moreproblems due to limitations and disadvantages of the related art.

[0022] An object of the present invention is to provide an in-planeswitching mode LCD device in which a dielectric frame having a smallerdielectric anisotropy than that of a liquid crystal or an electrodeframe is formed in a portion where an electrode is bent, so that theliquid crystal is exactly operated, thereby obtaining high response timeand preventing residual images from occurring.

[0023] Additional advantages, objects, and features of the inventionwill be set forth in part in the description which follows and in partwill become apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

[0024] To achieve these objects and other advantages and in accordancewith the purpose of the invention, as embodied and broadly describedherein, an in-plane switching mode LCD device according to the presentinvention includes: first and second substrates; common electrodesarranged on one of the first and, second substrates in a substantiallyzigzag pattern wherein each common electrode has at least one bentportion; pixel electrodes arranged with a substantially zigzag patterncorresponding to the common electrodes roughly in parallel with thecommon electrodes; common electrode frames extending from the bentportion; and a liquid crystal between the first and second substrates.

[0025] In another aspect of the present invention, an in-plane switchingmode LCD device includes: first and second substrates; common electrodesarranged on one of the first and second substrates in a substantiallyzigzag pattern; pixel electrodes arranged with a substantially zigzagpattern corresponding to the common electrodes roughly in parallel withthe common electrodes wherein each pixel electrode has at least one bentportion; a dielectric frame partially overlapping the bent portion ofthe pixel electrode and extending from the bent portion, having agradually decreasing width toward the common electrodes; and a liquidcrystal between the first and second substrates.

[0026] It is to be understood that both the foregoing generaldescription and the following detailed description of the presentinvention are exemplary and explanatory and are intended to providefurther explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this application, illustrate embodiment(s) of theinvention and together with the description serve to explain theprinciple of the invention. In the drawings:

[0028]FIG. 1 is a layout illustrating a related art in-plane switchingmode LCD device;

[0029]FIG. 2 is an enlarged view of a disclination region in the relatedart;

[0030]FIG. 3 is an enlarged view of a region where electric field isuneven in the related art;

[0031]FIG. 4 is a schematic view of an in-plane switching mode LCDdevice according to a first embodiment of the present invention;

[0032]FIG. 5 is a schematic view of an electrode frame region accordingthe first embodiment of the present invention;

[0033]FIGS. 6A and 6B are plan views of a dielectric frame regionaccording to a second embodiment of the present invention; and

[0034]FIGS. 7A and 7B are sectional views of the dielectric frame regionaccording to the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0036] An in-plane switching mode LCD device according to the firstembodiment of the present invention includes two substrates (not shown),common electrodes 41 formed on one of the two substrates in asubstantially zigzag pattern, a pixel electrode 42 arranged with asubstantially zigzag pattern corresponding to the common electrode 41roughly between the common electrodes 41 in parallel with the commonelectrode 41, and common electrode frames 43 projected to form at leasttwo domains around a portion where the common electrode is bent, thedomains controlling movement of a liquid crystal outside the bentportion of the common electrode. The bent portion of the commonelectrode is bent at an angle smaller than 180° in a substantiallyzigzag pattern of the common electrode 41. Pixel electrode frames 44project to form at least two domains around a portion where the pixelelectrode is bent, the domains controlling movement of a liquid crystaloutside the bent portion of the pixel electrode. The bent portion-of thepixel electrode is bent at an angle smaller than 180° in a substantiallyzigzag pattern of the pixel electrode 42. There is a liquid crystal 45between the two substrates.

[0037] The common electrode frames 43 are arranged in parallel with oneanother, and the pixel electrode frames 44 are also arranged in parallelwith one another.

[0038] The common electrode frames 43 are located between twoneighboring pixel electrode frames 44, and the pixel electrode frames 44are located between neighboring common electrode frames 43. The pixelelectrode frames 44 and the common electrode frames 43 are alternatelyarranged in one direction of a panel.

[0039] Each pixel electrode frame 44 and each common electrode frame 43do not contact a corresponding common electrode 41 and a correspondingpixel electrode 42.

[0040] The common electrode frame 43 is essentially located inside thebent portion of the pixel electrode 42, i.e., inside the angle smallerthan 180° formed by the bend in the pixel electrode. The pixel electrodeframe 44 is essentially located in a bent portion of the commonelectrode 41, i.e., inside the angle smaller than 180° formed by thebend in the common electrode.

[0041] In the aforementioned in-plane switching mode LCD device of thepresent invention, as shown in FIG. 5, the common and pixel electrodeframes 43 and 44 form at least two domains in a region where the commonelectrode 41 and the pixel electrode 42 are bent, i.e., a portion Dwhere the common electrode frame 43 or the pixel electrode frame 44 isformed. The domains serve to drive the liquid crystal 45 by means of theelectric field, so that the operation range of the liquid crystal isdriven not by the electric field, not by neighboring liquid crystalmolecules.

[0042] An in-plane switching mode LCD device according to the secondembodiment of the present invention will be described with reference toFIGS. 6A and 6B and 7A and 7B.

[0043] In the second embodiment of the present invention, the commonelectrode 41 and the pixel electrode 42 are arranged in a substantiallyzigzag pattern so as to prevent uneven electric field from occurring ina portion where the electrode is bent.

[0044] As shown in FIG. 6A, a dielectric frame 46 is formed to partiallyoverlap the pixel electrode 42 and includes a dielectric material havinga dielectric anisotropy smaller than that of the liquid crystal. Asshown in FIG. 6B, the dielectric frame 46 is formed to partially overlapthe common electrode 41 and includes a dielectric material having adielectric anisotropy greater than that of the liquid crystal.

[0045] In other words, in FIG. 6A, the dielectric frame 46 partiallyoverlaps the pixel electrode 42 in a portion where electric field isunevenly generated. The width of the dielectric frame 46 graduallydecreases toward the common electrode 41 to form a wedge shape.

[0046] In FIG. 6B, the dielectric frame 46 partially overlaps the commonelectrode 41 in a portion where electric field is unevenly generated.The width of the dielectric frame 46 gradually decreases toward thepixel electrode 42 to form a wedge shape.

[0047] The dielectric frame 46 reduces the density of the electric fieldso that the uneven electric field is minimized during driving of theliquid crystal.

[0048] The dielectric frame 46, as shown in FIG. 6A, is formed inside abent portion of the pixel electrode 42. The bent portion of the pixelelectrode 42 is bent at an angle smaller than 180° in a substantiallyzigzag pattern of the pixel electrode 42. Alternatively, the dielectricframe 46, as shown in FIG. 6B, is formed outside a bent portion of thecommon electrode. That is, outside the angle smaller than 180° in asubstantially zigzag pattern of the common electrode 41.

[0049] The dielectric frame 46, as shown in FIG. 7A, the dielectricframe 46 has a smaller thickness than the distance between a lowersubstrate 48 and an upper substrate 47.

[0050] By contrast, as shown in FIG. 7B, the dielectric frame 46 mayhave the substantially same thickness as the distance between the lowersubstrate 48 and the upper substrate 47 so that it can serve as aspacer.

[0051] As aforementioned, the in-plane switching mode LCD deviceaccording to the present invention has the following advantages.

[0052] The dielectric frame having a smaller dielectric anisotropy thanthat of the liquid crystal is formed in a portion where the electricfield is unevenly generated as it converges in a bent portion of theelectrode. This reduces the density of the electric field so that theuneven electric field is minimized during driving of the liquid crystal.In this case, high response characteristic can be obtained and residualimages can be prevented from occurring.

[0053] Likewise, the electrode frame is formed in a portion where theoperation range of the liquid crystal operated by driving itsneighboring liquid crystal not by the electric field exists, so that theliquid crystal can exactly be operated, thereby obtaining high responsetime and preventing residual images from occurring. Particularly, incase where the electrode frame is formed, it is possible to form atleast two domains that move the liquid crystal in a portion where theelectrode is bent.

[0054] The forgoing embodiments are merely exemplary and are not to beconstrued as limiting the present invention. The present teachings canbe readily applied to other types of apparatuses. The description of thepresent invention is intended to be illustrative, and not to limit thescope of the claims. Many alternatives, modifications, and variationswill be apparent to those skilled in the art.

What is claimed is:
 1. An in-plane switching mode liquid crystal displaydevice comprising: first and second substrates; common electrodesarranged on one of the first and second substrates in a substantiallyzigzag pattern wherein each common electrode has at least one bentportion; pixel electrodes arranged with a substantially zigzag patterncorresponding to the common electrodes roughly in parallel with thecommon electrodes; common electrode frames extending from the bentportion of at least one of the common electrodes; and a liquid crystalbetween the first and second substrates.
 2. The device of claim 1,further comprising: pixel electrode frames extending from a bent portionof at least one of the pixel electrodes.
 3. The device of claim 2,wherein respective common electrode frames are located between twoneighboring pixel electrode frames.
 4. The device of claim 2, whereinrespective pixel electrode frames are located between neighboring commonelectrode frames.
 5. The device of claim 2, wherein respective commonelectrode frames and the pixel electrode frames are arranged in parallelwith one another.
 6. The device of claim 5, wherein the pixel electrodeframes and the common electrode frames are alternately arranged in onedirection.
 7. The device of claim 1, wherein the common electrode framesare essentially located in the bent portion having a smaller angle than180°.
 8. The device of claim 2, wherein the pixel electrode frames areessentially located in the bent portion having an angle smaller than180°.
 9. An in-plane switching mode liquid crystal display devicecomprising: first and second substrates; common electrodes arranged onone of the first and second substrates in a substantially zigzag patternwherein each pixel electrode has at least one bent portion; pixelelectrodes arranged with a substantially zigzag pattern corresponding tothe common electrodes roughly in parallel with the common electrodeswherein each pixel electrode has at least one bent portion; a dielectricframe partially overlapping the bent portion of the pixel electrodes andextending from the bent portion; and a liquid crystal between the firstand second substrates.
 10. The device of claim 9, wherein the dielectricframe is formed inside the bent portion.
 11. The device of claim 9,wherein the dielectric frame has a gradually decreasing width toward thecommon electrodes.
 12. The device of claim 9, wherein the dielectricframe includes a dielectric material having a dielectric anisotropysmaller than that of the liquid crystal.
 13. The device of claim 9,wherein the dielectric frame has a thickness smaller than a distancebetween the first and second substrates.
 14. The device of claim 9,wherein the dielectric frame has a thickness substantially equal to adistance between the first and second substrates.
 15. An in-planeswitching mode liquid crystal display device comprising: first andsecond substrates; common electrodes arranged on one of the first andsecond substrates in a substantially zigzag pattern wherein each commonelectrode has at least one bent portion; a pixel electrode arranged witha substantially zigzag pattern corresponding to the common electrodesroughly in parallel with the common electrodes; a dielectric framepartially overlapping the bent portion of the common electrodes andextending from the bent portion; and a liquid crystal between the firstand second substrates.
 16. The device of claim 15, wherein thedielectric frame is formed outside the bent portion of the commonelectrodes.
 17. The device of claim 15, wherein the dielectric frame hasa gradually decreasing width toward the pixel electrodes.
 18. The deviceof claim 15, wherein the dielectric frame includes a dielectric materialhaving a dielectric anisotropy greater than that of the liquid crystal.19. The device of claim 15, wherein the dielectric frame has a thicknesssmaller than a distance between the first and second substrates.
 20. Thein-plane switching mode LCD device of claim 15, wherein the dielectricframe has a thickness substantially equal to a distance between thefirst and second substrates.